In the paper and plastic film industries, a dancer roll is widely used to maintain constant tension on a continuous web of raw material as the raw material unwinds in a conventional unwind system. More specifically, the unwind system typically uses an air-loaded or weight-loaded dancer bar, roll or festoon carriage to actively control the web tension from the top of a roll of raw material to its core. The conventional unwind system also uses a closed loop software program and a position sensor to determine the dancer or festoon carriage position and to adjust unwind spindle speed to maintain consistent position and through-roll web tension levels.
The conventional unwind method works well for materials with consistent machine direction (MD) stretch, tension and thickness. However, some MD elastomeric raw materials used to produce personal care products contain stretch, basis weight and thickness properties that change from the top of the roll to the core. These variable through-roll stretch properties affect material consumption, product size and fit and overall process control. Conventional unwinds will not compensate for variable MD elastomeric properties, which results in an increased raw material consumption, increased machine cull waste, and products that do not conform to target design criteria.
A process system is needed in the industry that compensates for varying MD elastomeric properties in order to reduce elastomeric material consumption, product variability and overall process variability and down time.